1. Field of Invention
The present invention relates to a broadband antenna, and more particular to a broadband antenna having a bandwidth adjustment portion for broadening the bandwidth thereof.
2. Related Art
Antenna is a coupling element or a conductive system used for converting electrical signals in a circuit into electromagnetic energy in the air, and vice versa. When transmitting signals, the antenna converts the electrical energy of a radio frequency into electromagnetic energy for being radiated to the surrounding environment. When receiving signals, the antenna receives and converts the electromagnetic energy into the electrical energy of a radio frequency for being processed in a receiver.
Wireless communication standards all have a transmitting/receiving end, and an antenna is required to covert radio waves in the air into electrical signals no matter in the process of reception or transmission. To match a gradually scaled down mobile device mechanism, the appearance and volume of the antenna become increasingly compacted. For example, in the very beginning, the antenna for a cell phone is exposed to the outside, and later is shrunk in the phone. Moreover, as the size of the cell phone is gradually reduced, the exposed portion of the antenna changes from a protrusion of 5 to 10 cm to less than 3 cm, and is further integrated into the circuit board afterwards.
However, as different wireless communication standards generally have different wavelengths, the transceiver may be designed as common, but the antenna must be fabricated according to actual requirements. Under the current trend of increasingly higher integration and the miniaturization of system mechanism, appropriate antenna designs and combinations of various types of antennae are the key to the product performance.
In view of the cost, the antenna of a wireless product is usually in the form of a flat panel antenna, which often has an insufficient bandwidth due to limits on the area and PCB characteristics. Besides, the bandwidth may affect the yield and performance of the wireless product. Therefore, limited by the area of the antenna, it is a critical manner to broaden the bandwidth of the antenna to improve the yield and performance of the wireless product.